Manufacture of sheathing lumber from redwood bark



. Patented Mar. 24, 193i UNITED STATES 'PATENTI OFFICE".

' urea 12. .naame, or nanvnnn, ILLINOIS, assreivonro 'PAcna-Ic Lmnaconrumor cnrcaeo, ILLINOIS, a CORPORATION or mm MANUFACTURE OI BREATHINGIIUMBEB FROM REDWOOD BARK- Io Drawing.

The present invention relates to a process for the conversion of thebark of the redwood or Sequoia tree into commercial forms of sheathinglumber, wall board and the like.

One '0 the objects of the invention is to convert the bark into saidsheathing lumber while retainin the entire tannin content of the bark sot at the same may have enhanced durability and resistance to fire andwood-destroying insects, the further object being to improve thewater-proofing qualities ofthe said board.

This process comprises the treatment of the bark from redwood trees.These trees,

which grow to enormous heights, are the largest trees in the world, andhave bark that averages from 8 to 27 inches in' thickness. The bark isalmost incombustible and contains a material apparently very repulsiveto zo insects, so that in the forests where these trees grow there is nobird life, because there are no insects upon which the birds may feed.This property of redwood bark is taken advantage of in the process forproducing a 85 sheathing board or lumber wh1ch will be proof against theinroad of rodents, termites,

and ants and other wood-destroying insects.

In thisrespect the material is unique. It is also'inherentlyfire-resistant and is said to burn .only with considerable difiicultyand not to be a free. su porter of combustion, so

that board made t erefrom does not represent the same fire hazard asdoes board made from bagasse fibres. While not burning terial when onceignited shows a distinct tendency to smolder, acting in this respectveiy much like punk.

'ormerly it was the custom to fell the'trees in the woods and to barkthem at that point, and eventually after the bark had dried outsuifioiently to burn it up with branches and other wood waste. Thishowever, was quite a task and the recent perfection of lumberingoperations enables the transportation of felled trees with their barkabout them directly to the lumber mill. At this point the trees ared'e-barked by mechanical means, Heretofore, theonly uses made of thismaterial have been attempts to burn it in the with a free flame,itappears that the ma-' the fibre and in the finishe therefrom. Incarrying out the process of 100 Application and June 22, 1929. Serial110. 878,058.

woods,'or else to make it into a rough sort of board, as disclosed inthe patent to John K.

.Shaw, No. 1,468,036, which makes a board,

the outside of which consists of shredded redwood'bark and the inside ofwhich consists i of bagasse fibres. Another patent, N 0. 1,349,112 of H.P. Weiss, makes a mat of the fibres of the redwood in their originallength covered with a covering materlal, such as canvas, and then tiedtogether into bundles. 6o

' The present process is quite distinct from what is shown in either ofthese two patents,

'as it leads to the production of a board in which the fibres arecomparatively strongly compressed so as to produce a sheathing 05 board.

As an exemplification of the manner in which the process is to becarried out, it may be stated that after the felled logs arrive at thelumber mill they are mechanically debarked so as to separate the barkfrom the wood of the trees. This bark is then run through the regularstandard hogging mill which converts itinto comparatively smallindividual chi s which are then passed 7 through a shre ding devicewhich may also be of standard manufacture, in order to pro. duce acomparatively loose shredded product.

In my co-pending application Serial No. 37 2,224, filed June 19, 1929, Ihave described 0 a process for the conversion of redwood bark intosheathin lumber wherein the bark is treated for t e removal therefrom ofan associated material which .for want of a better name I havedesignated as tree sand and wherein the fibres of the bark are treatedunder pressure with an alkaline solution for "conversion into a fibrefrom which wall board or sheathing board may be manufactured. In thesaid co-pending application 'I have be also described thepreliminary-treatment of; the bark by means of leaching in water inorder to remove therefrom the therein contained tannin and tannic acidand its recoverg y my present invention, however, I do not attempt toremove the said tannin, but. prefer the same substantiall unchanged inproduct made my present invention, I proceed as follows I employ as theraw material, the bark of the trees' after the hogging of the same, asabove described, or just as it is removed from the logs'when theyarriveat the lumber mill. In that case the bark is first cut into lengths ofsuch size that they may readily be fed into a machine which reduces thebark to an open or shredded condition. The slabs of 1 bark are then fedinto the shredding machine in such manner that the fibresin the o positedirection to the mechanism, for b t us operating the material isshredded ut the fibres are not torn, cut or broken.

As already mentioned there is associated with the fibre a smallquantity'of a raw material consisting of'little' round black particleswhich Ihave designated as tree sand.

20 For the preparation of a proper type of sheathing board it isdesirable to remove this tree sand. The shredding operation justdescribed serves to loosen this tree sand which may then be removed fromthe sepa- 25 rated and loosened'fibres by a dry screening operation.After passing through a screening machine, wherein the tree sand passingthrough the gyratini, oscillating or rotating sieve is thus mec anicallyseparated so from the fibres, the latter are then run through through adefiberingmachine which further loosens the fibres and separates thesame more-completely. This operation consists in passing the materialbetween two rapas idly revolving plates in the presence of a substantialamount of water, the mixture of water and fibres leaving being run intovats rovided with agitatin means whereupon a ditional water is addeuntil the ratio of stock to water is such as to roduce a substantiallyuniform freely flowing suspension. This suspension of fibre is thenpassed over wet screens having interstices fine enough to retain thefibre but coarse enough to pass the residual tree sand although analternative method is to pass the same through rifile tanks where thefibre is kept in suspension but the tree-sand is allowed to settle out.

Havin thus obtained a sus nsion of comparative y pure fibres free romthe treesand these fibres are then subjected to digestion underpressure'in a 'solution contaimng a chemical ca able of combining withthe tannin containe in the bark fibres, and some of which tannin existsin solution in the liquid nsion. It has been capable of forminfiaportions of the sus ound that a chemic colorless insoluble tannate isparticularly mains unchanged with the further advantage that the a.waste liquors resulting from t e digestor are practically water whiteand may be run into screens without causing golution.

. 65. In order to carry out this step 0 t e invenath of the shred ing'the said machine {insects and other wood-attac sirable as thereby thecolor of the fibre 'retion there is employed a solution of aluminumsulphate or its equivalent such as antimony or other chemical saltcapable of forming colorless insoluble tannates. The best results areobtained by employing a solution of aluminum sulphate'of ,4 strength towhich at a pressure of 75 pounds above atmospheric. The percent ofstrength and time of pressure give are not to be constructed as limitingbut are ven as an illustration of one of the best the fibres aresubjected while contained in a steam tight digester for a period of twohours met ods of carrying out the invention. The

After the digestion is complete, the pressure is-blown off the digester,and its contents dischar ed into a tank where they are diluted with aditional water and then are freed from the liquid portions of theresulting suspension by a screening operation such as, for example, bypassing the fibres over Oliver =filters or similar chemical filtration-.ment.

uifip- The fibres are washed on the slfiil lters and are then placed ina heater and treated therein with a size such as alum and board formingmachine, as i well known in rosin soap, and are then passegover astandard the art of formation of bo rd from other fibres. I

The solution se arated from the fibres need not be discarded utafter an'anal sis to determine the residual aluminum 'su phate, or

other chemical, therein, may bev refortified with the same chemical tobring it up to the initial strength of one-half percent.

The board resulting from this process is of a pleasing brown color andhas an rior me- .chanical strength to one made by t e alkaline digestionprocess. The nature of the redwood bark, which is inherentl resistant tovermin, renders the sameparticularl va uable vfor use in such parts ofthe wor d where wooddestroyinginsects live. The board is particularlyuseful for sheathing and ma also be employed-=for wall board, as itreadl y takes the coating of plaster, cement or stucco.

While I have described the use of aluminum sulphate specifically I.again wish to point out that otherequivalent chemicals capable offorming substantially colorless tannates may be emplogad such forexample as an antimony salt. f course, if color is desired, I may alsoem loy such salts as oo 'per sulphate. In suc ca however, operationcould not be carried out in an iron a paratus unless the' same werecopper ated or otherwisetreated to' revent the gemoval of the, copperfrom the so ution. For

all practical purposes aluminum sulphate is the cheapest and thereforethe most desirable.

The exact sequence of the operations, espethan cotton flock and usefulas a filler in plastic materials. I desire to include within the scopeof my invention the utilization of the fibresfor such purposes as well.

The essential feature of the resent invention resides'in the *di estiono the bark in a solutionof a ,chemica capable of forming an inspllublecompound with the tannins in the What I claim is:

1.v Individual fibres of redwood bark containing the insoluble tannateof the tannin compounds present in redwood bark.

2. The process of treating redwood bark for the separation of the fibresthereof which comprises boiling saidbark in a solution of a salt ca ableof forming insoluble tannates.

3. e process of treating redwood bark for the separation of the fibresthereof which comprises boiling said bark in a solution of a saltcapable of forming colorless insoluble tannates.

4. The process of treating redwood bark for the separation of the fibresthereof which comprises boiling said bark in a solution of aluminumsulphate. v

5. The process of treating redwood bark for the separation of the fibresthereof which com rises boiling said bark in a solution contaimn ofaluminum sulphate.

6. e process of prepann sheathing boards from redwood bark whiccomprises comminuting said bark, dry-sieving the therein containedtree-sand? t grinding the fibres thereof in water, thereupon wet-sievingthe fibres to remove the balance of the tree-sand therefrom, andthereupon boiling saidfibres under ressure in a solution of a chemicalcapable o formin insoluble tannates, washing-said boiled res and sizingthe same and o orless insoluble tannates, washing said boiled fibres andsizing pact board therefrom, and dryingan mg the latter.

8. The process of preparingl sheathing boards from redwood bark whiccomprises comminuting .said bark, dry-sievin most of the thereincontained tree-sand erefrom, grinding the fibres thereof in water,thereupon wet-sieving the fibres to remove the balance of the tree-sandtherefrom, and thereupon boiling said fibres under pressure in-asolution of aluminum sulphate, washing said boiled fibres and sizing thesame and forming a. compact board therefrom, and drying an seasoning thelatter.

9. The process of preparin sheathing boards from redwood bark whiccomprises comminuting said bark, dry-sievin most of the thereincontained tree-sand t erefrom,

grinding the fibres thereof in water, thereupon wet-sieving'the fibresto remove the balance of the tree-sand therefrom, andthereupon boilingsaid fibres under pressurein a solution of aluminum sulphate; washingsaid boiled fibres and sizing the same and formin a compact boardtherefrom, and drying an seasonin the latter.

'10; Sheathing fibres containing insoluble com ounds of the tanninspresent in natural red 00d bark.

ard comprising redwood the same and forming a coinseason- In witnesswhereof, I have hereunto'subscribed my name. A

-- ELTON R. nARLIN most of v erefrom,

rming a compact board therefrom, and drying and seasoning the latter.

- 7. The process of' preparing sheathing boards from redwood bark whichcomprises comminuting said bark, dry-sievin most of the thereincontained tree-sand t erefrom,

grinding the fibres thereof in water, thereupon wet-sieving the fibrestorem ove the bal-,

ance of the tree-sand therefrom,and thereupon boiling said fibres underPressure in a solution of a chemicalcapable o forming col- 7

